1. Field of the Invention
This invention relates in general to a cantilever mount of a substrate lamina of a surface wave device wherein the device may be generally triangular shaped and is attached to a base along one edge thereof and wherein its point which extends from said edge of attachment is mounted above the base so that it can freely move.
2. Description of the Prior Art
Surface wave components are known which may be filters, resonators and/or delay lines. The significant features of such components comprise a transducer and/or reflector structures which are arranged on the surface of the substrate plate so as to essentially define the prescribed properties of the component. The structures may be strip-shaped finger electrodes and/or reflector strips attached to the surface as well as auxiliary structures such as pads, or shielding electrodes. Electrically, non-conducting etched structures of the substrate surface are also standard for reflector structures instead of metallic strips.
Such a substrate lamina of, preferably, quartz, lithiumniobat, lithiumtantalat and the like is normally held on a support and is accommodated in a housing, where an adhesive means is provided for mounting and is arranged between the back surface of the substrate lamina on the opposite side of the wave components and the support. Generally, the adhesive extends over the entire surface of the back surface of the substrate lamina so as to provide a tight attachment of the substrate lamina to the support.
An adhesive means which is relatively plastic is the preferred means of attaching such lamina to a support so that the stresses occurring due to temperature changes for example, in the support are isolated from the substrate lamina. Gaseous discharge from such a viscous adhesive combined with the corresponding precipitate on the substrate surface of the substrate lamina carrying the structures have been assumed as the reasons that disturbances occur which have occurred in the past, but these cannot be eliminated using glues having less solvent or less softener and which are harder have also been employed.
Disturbances occur to a noticeable degree particularly in narrow band filters and resonator components and/or delay lines where the disturbances are based on mechanical movement which originate from housing parts, for example.
U.S. Pat. Nos. 3,753,164 and 4,450,420 disclose surface wave filters having trapezoidal or triangular-shaped substrate lamina. The shapes selected serve the purpose for reducing reflections and of saving substrate material. The employment of a substrate body having a triangular shape is known from the publication 1983 Ultrasonics Symposium, page 268, FIG. 4. This article discloses a dynamometer having a surface wave structure mounted on the surface of the substrate body. This structure supplies the output measured variable. The surface wave structure is at least substantially placed therein as shown in FIG. 4 close to the edge of the three-sided substrate body where the substrate body is held. The point lying opposite the mounting is largely free of a structure.
European Patent Application Publication No. 0 156 502 discloses a surface wave arrangement having a rhombic shape. The rhombus is held in its middle region which is where the main part or the defining part of the surface wave structure is located. "Defining part" is defined as those parts of the transducers and/or reflector structure which significantly define the prescribed properties of the surface wave device. The central position of such a structure thus determines a certain limiting region from which the defining properties of the structure greatly diminish relative to the center of the structure toward the end which is held.